44 Journal of Comparative Neurology. 



of the diencephalon accords with the phylogenetic, as it pre- 

 sents itself here. Let us summarize the characteristics of this 

 brain region in Protopterus : A long stalked pineal which pene- 

 trates the cartilaginous roof, with its vesicle, a simple but 

 slightly folded velum, a vascular plexus not yet differentiated into 

 any particular organ, which together with the remaining tela ap- 

 pears from a superficial consideration to make a vesicular organ, 

 plexus inferiores lying laterally. All these characteristics point 

 to a close connection between the brain of Protopterus and that 

 of selachians, while the degeneration of the pineal, and the dif- 

 ferentiation of the vascular plexus into a particular organ, are 

 points which together with the differentiation of the velum and 

 plexus inferiores, and the elaboration of the roof segments, lend 

 a peculiar character to the amphibian brain from Gymnophion 

 to the Anura, and cause me to assume that their relation to 

 Protopterus is more distant than that of Protopterus to the 

 selachians. In concluding Burckhardt calls attention to the 

 fact that the earlier brain-anatomists (and Gegenbaur in his text- 

 book) considered the brain cleft ("Gehirnschlitz") the criterion 

 for determining relations. We now know that the Gehirnschlitz 

 is an opening which arises when through gross methods of pre- 

 paration the interesting roof of the diencephalon is removed. 



His (jS-9 2 ) from an examination of profiles of various 

 embryonic brains shows that epiphyses may arise at more than 

 two places. He says: The choroidal node found by Gotte at 

 the cephalic margin of the diencephalon in Amphibia belongs to 

 the category of cephalic epiphyses. Here it is easy to distin- 

 guish them, as the difference between the two is very great. 

 The epiphyis of selachians also arises from the cephalic part of 

 the roof of the diencephalon. Later, however, almost the 

 whole diencephalic roof is elevated and there results the famil- 

 iar projection included between fore-brain and mid-brain, whose 

 base extends caudad nearly to the post-commissure. Similar 

 conditions prevail in teleosts. His also studied an epiphysis 

 of the cephalic roof of the diencephalon in a human embryo 

 10.5 mm. in length. The roof plate forms at this stage a small 

 medi an longitudinal ridge with two lateral angles. Cephalad 



